forkfd: introduce forkfd_wait4() that takes options

"wait4" because it looks like the wait4() BSD function, which has the
signature:

       pid_t wait4(pid_t pid, int *wstatus, int options,
                   struct rusage *rusage);

And because ours also has 4 parameters.

Having options is important anyway. I might want to add some more later,
but we can't really support them with the fall back implementation (in
fact, we don't honor WNOHANG in the fall back implementation either).

Change-Id: I4e559af2a9a1455ab770fffd15f5858bb357e15b
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>

4 files changed, 56 insertions, 22 deletions

diff --git a/src/3rdparty/forkfd/forkfd.c b/src/3rdparty/forkfd/forkfd.c
index 31189fa2cd..795aa9dd68 100644
--- a/src/3rdparty/forkfd/forkfd.c
+++ b/src/3rdparty/forkfd/forkfd.c
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 Intel Corporation.
+** Copyright (C) 2020 Intel Corporation.
 ** Copyright (C) 2015 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com
 **
 ** Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -94,7 +94,7 @@
 
 static int system_has_forkfd(void);
 static int system_forkfd(int flags, pid_t *ppid, int *system);
-static int system_forkfd_wait(int ffd, struct forkfd_info *info, struct rusage *rusage);
+static int system_forkfd_wait(int ffd, struct forkfd_info *info, int ffdwoptions, struct rusage *rusage);
 
 #define CHILDREN_IN_SMALL_ARRAY     16
 #define CHILDREN_IN_BIG_ARRAY       256
@@ -225,6 +225,16 @@ static void convertStatusToForkfdInfo(int status, struct forkfd_info *info)
     }
 }
 
+static int convertForkfdWaitFlagsToWaitFlags(int ffdoptions)
+{
+    int woptions = WEXITED;
+    if (ffdoptions & FFDW_NOWAIT)
+        woptions |= WNOWAIT;
+    if (ffdoptions & FFDW_NOHANG)
+        woptions |= WNOHANG;
+    return woptions;
+}
+
 static int tryReaping(pid_t pid, struct pipe_payload *payload)
 {
     /* reap the child */
@@ -800,14 +810,13 @@ out:
 }
 #endif // _POSIX_SPAWN && !FORKFD_NO_SPAWNFD
 
-
-int forkfd_wait(int ffd, struct forkfd_info *info, struct rusage *rusage)
+int forkfd_wait4(int ffd, struct forkfd_info *info, int options, struct rusage *rusage)
 {
     struct pipe_payload payload;
     int ret;
 
     if (system_has_forkfd())
-        return system_forkfd_wait(ffd, info, rusage);
+        return system_forkfd_wait(ffd, info, options, rusage);
 
     ret = read(ffd, &payload, sizeof(payload));
     if (ret == -1)
@@ -846,10 +855,11 @@ int system_forkfd(int flags, pid_t *ppid, int *system)
     return -1;
 }
 
-int system_forkfd_wait(int ffd, struct forkfd_info *info, struct rusage *rusage)
+int system_forkfd_wait(int ffd, struct forkfd_info *info, int options, struct rusage *rusage)
 {
     (void)ffd;
     (void)info;
+    (void)options;
     (void)rusage;
     return -1;
 }
diff --git a/src/3rdparty/forkfd/forkfd.h b/src/3rdparty/forkfd/forkfd.h
index fe70371719..205928cc2b 100644
--- a/src/3rdparty/forkfd/forkfd.h
+++ b/src/3rdparty/forkfd/forkfd.h
@@ -44,13 +44,20 @@ extern "C" {
 
 #define FFD_CHILD_PROCESS (-2)
 
+#define FFDW_NOHANG             1       /* WNOHANG */
+#define FFDW_NOWAIT             2       /* WNOWAIT */
+
 struct forkfd_info {
     int32_t code;
     int32_t status;
 };
 
 int forkfd(int flags, pid_t *ppid);
-int forkfd_wait(int ffd, struct forkfd_info *info, struct rusage *rusage);
+int forkfd_wait4(int ffd, struct forkfd_info *info, int options, struct rusage *rusage);
+static inline int forkfd_wait(int ffd, struct forkfd_info *info, struct rusage *rusage)
+{
+    return forkfd_wait4(ffd, info, 0, rusage);
+}
 int forkfd_close(int ffd);
 
 #if _POSIX_SPAWN > 0
diff --git a/src/3rdparty/forkfd/forkfd_freebsd.c b/src/3rdparty/forkfd/forkfd_freebsd.c
index 77ce3fcfad..c4ca796ccd 100644
--- a/src/3rdparty/forkfd/forkfd_freebsd.c
+++ b/src/3rdparty/forkfd/forkfd_freebsd.c
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 Intel Corporation.
+** Copyright (C) 2020 Intel Corporation.
 **
 ** Permission is hereby granted, free of charge, to any person obtaining a copy
 ** of this software and associated documentation files (the "Software"), to deal
@@ -29,6 +29,10 @@
 
 #include "forkfd_atomic.h"
 
+// in forkfd.c
+static int convertForkfdWaitFlagsToWaitFlags(int ffdoptions);
+static void convertStatusToForkfdInfo(int status, struct forkfd_info *info);
+
 #if __FreeBSD__ >= 10
 /* On FreeBSD 10, PROCDESC was enabled by default. On v11, it's not an option
  * anymore and can't be disabled. */
@@ -81,19 +85,23 @@ int system_forkfd(int flags, pid_t *ppid, int *system)
     return ret;
 }
 
-int system_forkfd_wait(int ffd, struct forkfd_info *info, struct rusage *rusage)
+int system_forkfd_wait(int ffd, struct forkfd_info *info, int ffdoptions, struct rusage *rusage)
 {
     pid_t pid;
     int status;
-    int options = WEXITED;
+    int options = convertForkfdWaitFlagsToWaitFlags(ffdoptions);
 
     int ret = pdgetpid(ffd, &pid);
     if (ret == -1)
         return ret;
-    ret = fcntl(ffd, F_GETFL);
-    if (ret == -1)
-        return ret;
-    options |= (ret & O_NONBLOCK) ? WNOHANG : 0;
+
+    if ((options & WNOHANG) == 0) {
+        /* check if the file descriptor is non-blocking */
+        ret = fcntl(ffd, F_GETFL);
+        if (ret == -1)
+            return ret;
+        options |= (ret & O_NONBLOCK) ? WNOHANG : 0;
+    }
     ret = wait4(pid, &status, options, rusage);
     if (ret != -1 && info)
         convertStatusToForkfdInfo(status, info);
diff --git a/src/3rdparty/forkfd/forkfd_linux.c b/src/3rdparty/forkfd/forkfd_linux.c
index 27ab09f748..87acdc3341 100644
--- a/src/3rdparty/forkfd/forkfd_linux.c
+++ b/src/3rdparty/forkfd/forkfd_linux.c
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 Intel Corporation.
+** Copyright (C) 2020 Intel Corporation.
 **
 ** Permission is hereby granted, free of charge, to any person obtaining a copy
 ** of this software and associated documentation files (the "Software"), to deal
@@ -51,6 +51,10 @@
 #  define P_PIDFD       3
 #endif
 
+// in forkfd.c
+static int convertForkfdWaitFlagsToWaitFlags(int ffdoptions);
+static void convertStatusToForkfdInfo(int status, struct forkfd_info *info);
+
 static ffd_atomic_int system_forkfd_state = FFD_ATOMIC_INIT(0);
 
 static int sys_waitid(int which, int pid_or_pidfd, siginfo_t *infop, int options,
@@ -162,15 +166,20 @@ int system_forkfd(int flags, pid_t *ppid, int *system)
     return pidfd;
 }
 
-int system_forkfd_wait(int ffd, struct forkfd_info *info, struct rusage *rusage)
+int system_forkfd_wait(int ffd, struct forkfd_info *info, int ffdoptions, struct rusage *rusage)
 {
     siginfo_t si;
-    int options = WEXITED | __WALL;
-    int ret = fcntl(ffd, F_GETFL);
-    if (ret == -1)
-        return ret;
-    if (ret & O_NONBLOCK)
-        options |= WNOHANG;
+    int ret;
+    int options = __WALL | convertForkfdWaitFlagsToWaitFlags(ffdoptions);
+
+    if ((options & WNOHANG) == 0) {
+        /* check if the file descriptor is non-blocking */
+        ret = fcntl(ffd, F_GETFL);
+        if (ret == -1)
+            return ret;
+        if (ret & O_NONBLOCK)
+            options |= WNOHANG;
+    }
 
     ret = sys_waitid(P_PIDFD, ffd, &si, options, rusage);
     if (ret == -1 && errno == ECHILD) {